In the wire and cable industry, two or more insulated conductors can be twisted together to form twisted conductors. Twisted conductors, in particular a twisted pair of conductors, are the basic component of many types of multi-conductor cables. The manufacture of a twisted pair is accomplished through the use of a machine called a “bow twinner” or pairing machine, and while there are several ways in which two conductors can be twisted together, one method has enjoyed widespread popularity. In this method, the individual conductors are fed from stationary spools or pay-offs through guides to a take-up reel that is mounted inside of a gimbal-like assembly or cradle about which rotates a member called a bow. The bow is rotated about an axis along which the insulated conductors are fed from the spools to effect a twisting of the wires before they are wound on the take-up reel. One machine which operates in this manner is shown and described in U.S. Pat. No. 3,945,182, the disclosure of which is herein incorporated by reference in its entirety.
One test that the twisted pair must pass prior to shipment or use in other multi-conductor cables is an insulation test in which a high electrical potential is applied between the surface of the insulation and the conductors. If the insulation is defective because of, for example, an insulation break caused by the twisting process, a spark will jump from the point of application through the defect to the conductor. Such testing is commonly called “spark testing” by which defects in the insulation can be sensed, counted and measured through the pulse of current manifested by the spark.
It is most desirable to spark test the twisted pair as they are wound on the take-up reel in order to save time and keep productions costs down. However, the only place that the wires exist as a twisted pair is inside the rotating bow, just before they are wound on the take-up reel. This presents certain problems in the spark testing of the wire.
One problem is that the high potential test electrode must be inside the bow, where space is limited, and there can be no directly wired connections to the electrode because of the bow rotation around the test components mounted on a cradle of a twinner. Since the bow rotates around a cradle of a twinner where test components are located, any power or control wiring must be brought to the cradle using slip ring assemblies through the shaft around which the bow rotates. Space limitations on existing machines dictate that only two low voltage slip rings are available for this purpose. A device of this type is described in U.S. Pat. No. 4,056,771, the disclosure of which is herein incorporated by reference in its entirety. Prior to this, because of the many functions a spark tester may be called upon to serve, earlier designs for spark testers had controls and indicators inside the twinning bow. Adjustment of the spark tester controls was inconvenient and time consuming because the high inertia machinery had to be stopped each time an adjustment was made and then restarted.
Controlling a spark tester through slip ring assemblies provides a solution to this problem, but imposes limitations to the successful application of the test equipment. Retrofitting existing machinery to add a spark tester was very difficult because if the necessary slip rings were not available, adding them required extensive machinery modifications which are costly and difficult. Spark testers, when located within the bow of a twinner, have traditionally required up to three slip ring assemblies. Most often the equipment had to be designed and built to incorporate the spark tester. Slip rings are subject to wear and require regular maintenance. Often they do not provide uninterrupted signal contact, thereby resulting in poor spark tester performance.
The present invention overcomes these difficulties by locating all controls and indicators at a suitable remote location, outside of the rotating mechanism, so that adjustments can be made as the machinery is operated, and by locating the high potential components and fault detection circuitry within the rotating mechanism, and energizing these components using power already available within the mechanism. Communication between the control portion and the high voltage fault detector is accomplished by use of radio frequency serial transceivers. Other objects of the invention are to utilize available power within the rotating mechanism to eliminate the need for retrofitting a twinner with dedicated and costly slip ring assemblies.
Accordingly, it is an object of the present invention to provide a spark tester and method of use which overcomes the above-mentioned drawbacks and disadvantages associated with the operation of a spark tester within the rotating bow of a twinner.